The present invention relates generally to peristaltic pumps that are preferably used to pump viscous and/or polluted media.
Peristaltic pumps or hose pumps consist of a generally cylindrical housing in which an elastic or flexible hose is placed and arranged in a loop against a portion of the cylindrical wall, whereby the hose is typically arranged in a loop of about 180xc2x0. The hose forms a volume that is divided into a number of pump chambers by a pump unit that is arranged for rotation on a centrally positioned shaft in the housing. The pump unit supports one or more rollers or slide shoes that engage the hose and compress it to thereby divide the hose into suction and pressure chambers, respectively. On rotation of the pump unit, the rollers gradually transport the medium from an inlet to an outlet through peristaltic action. A major advantage of such a pump is that no parts of the pump other than the hose are in contact with the pumped medium, and for this reason hose pumps are used within many areas where this is of importance, from pumping sterile liquids in the medical field, for instance, to pumping polluted and/or aggressive media or sludge within the industry and other fields.
Typically, in all such applications the pump unit is provided with at least two rollers or slide shoes, thereby eliminating the need for non-return valves. An embodiment of this type is disclosed for instance in NO 144 977. However, the problem with such pumps is that the number of compressions of the hose during one revolution of the pump unit increases as the number of rollers increases, and that the useful life of the hose is thus reduced correspondingly.
In order to increase the useful life of the hose, it is suggested in SE 357 801 that the hose is arranged in a loop of up to 360xc2x0, with the two ends of the hose positioned on top of each other. The hose is acted on by one single roller having a corresponding length or height and consequently continuously engaging the hose. In this way, the need for non-return valves is eliminated, and at the same time the useful life of the hose may in theory be doubled as compared to a pump having two rollers.
The peristaltic pumps available on the market all focus on optimizing certain parameters that are important to the intended use. Thus, pumps to be used for example in the medical field are designed for low pressure ranges, and generally also with a low suction capacity. The employed hoses are generally made of a homogenous material, without reinforcement. Instead, priority is given to other features, such as exact dosing, sterility etc.
On the other hand, pumps that are employed in industry and within the building sector, for example for pumping concrete, are dimensioned for high pressure ranges to transport the respective medium a longer distance or to a greater height. However, they are practically always stationary and the pumped medium is supplied to the pump in such way that no powerful suction capacity is needed Since the pumps are stationary, they are moreover of a comparatively heavy and bulky design and thereby basically not suited for use in the field, such as for clean-up operations in nature.
A considerable contributory cause to the heavy and unwieldy design is the high demand for tightness of the pump housing, which is a consequence of the fact that the pumps are traditionally filled with a liquid lubricant, for example glycerine.
Furthermore, the hose of such pumps is designed to withstand the relatively high pumping pressures without rupture or excessive, elongation. An example of such a hose is given in U.S. Pat. No. 3,887,306, where a hose is described that, in addition to a conventional tensile rigid reinforcement consisting of wires crossing one another at a suitable angle, in certain areas is provided with a reinforcement consisting of reinforcing threads arranged in the longitudinal direction of the hose. This longitudinal reinforce Kent is positioned in the area where the rollers engage the hose and likewise has the purpose of preventing excessive elongation of the hose by the action of the rollers against the latter.
A peristaltic pump using pairs of rollers to compress the hose is described in EP 0 889 237 A2. According to this document is suggested a hose design that shall be very durable and in particular shall exhibit great resistance to the local stress imposed on it by the rollers. To achieve this, it is suggested that the hose be made entirely of one and the same rubber material that shall be resistant to wear and weather. In the rubber material, four layers of reinforcement are embedded that are all of the same general structure, having parallel wires of synthetic fibre cord that are preferably helically arranged around the hose. These cord layers solely aim to increase the durability of the hose and do not significantly contribute to alter the pumping properties thereof.
However, to our knowledge there has been no development aiming at optimizing this type of peristaltic pumps in order to make them more easy to handle and more suitable for mobile use.
The present invention eliminates the above drawbacks in an efficient and appropriate way.
A general object of the invention is to produce a practically useful solution to the problem of providing a light and easily maneuverable peristaltic pump that has optimized operational features and useful life.
Accordingly, a basic object of the invention is to find an easy and appropriate way of minimizing the weight and dimensions of a peristaltic pump while simultaneously optimizing its suction capacity as well as its discharge pressure capacity.
According to the invention, this is achieved by arranging a guide path against an inner wall of the pump housing, the guide path being provided with an upper surface adapted for supporting the hose and the guide track being impregnated with a lubricant. Hereby, the dimensions of the pump housing can be considerably reduced since it does not have to be made extremely tight to enclose a major amount of free-flowing lubricant, as is conventional.
According to one embodiment of the invention the guide path consists of cellular rubber forming a reservoir for the lubricant, whereby a further improved, long-term interval lubrication is achieved.
According to other embodiments the guide path consists of a support ramp having an upper surface that is formed with a slope for positioning the ends of the hose in planes above each other, the slope is formed as a screw pitch and the roller and the inner wall of the pump housing are provided with layers of a resilient material, such as polyurethane.
According to other embodiments of the invention the length of a roller arm that in the outer end carries a roller for compressing the hose, is linearly adjustable in a radial direction, and a special hose coupling is used to perform a retraction of the hose towards the pump housing during assembly. All of these embodiments contribute to facilitate mounting and dismounting of the very rigid and thick hose in the pump.
According to further embodiments of the invention, the hose of the pump is formed of different layers to adapt it to the intended application. According to the invention, these layers consist of inner and outer layers of rubber material adapted to be resistant to the substances and to the influence they may be subjected to, as well as of compression rigid and tensile rigid reinforcement layers, respectively (referred to below as xe2x80x9ccompression rigidxe2x80x9d and xe2x80x9celongation rigidxe2x80x9d layers) and a thick layer of highly resilient or elastic material having low attenuation, serving as the xe2x80x9cmusclexe2x80x9d of the hose to achieve the desired suction capacity of the peristaltic operation and being arranged between said inner and outer layers. Thereby, is obtained a pump that may so to speak be tailored for different situations requiring optimized suction, pressure and physical properties.
According to still another embodiment the compression rigid reinforcement layer consists of cord material having cord of macrofilament crossing at an angle of about 120xc2x0, each at an angle of about 60xc2x0 to the central axis of the hose, and the elongation rigid reinforcement layer consists of tensile rigid cord material of polyester cord crossing at an angle of about 108xc2x0, each at an angle of about 54xc2x0 to the central axis of the hose. Such an embodiment optimizes the resistance to elongation of the hose as well as its ability to spring back and to withstand compression.
According to another embodiment of the invention, the different layers of the hose are arranged in an optimal order to provide the best efficiency possible. Outside the inner durable layer consisting of a first synthetic material, is arranged a first layer of the compression rigid cord material, then the layer of highly elastic material, a second layer of the compression rigid cord material and, adjacent to the outer durable layer consisting of a second synthetic material, the layer of elongation rigid cord material.
According to a further embodiment of the invention, the hose is dimensioned to provide maximum suction capacity while accepting solid particles of considerable size in the pumped medium, without being damaged thereby. For this purpose it exhibits a relationship between inner and outer diameter of  less than 0.56 and the layer of highly elastic or resilient material has a thickness of at least about 30% of the thickness of the hose wall.
Further embodiments of this first aspect of the invention are specified in the corresponding, dependent claims.
According to another aspect of the invention, it is suggested to use a pump according to the invention in mobile equipment for clean-up operations in remote areas.
According to yet another aspect of the invention a guide path is suggested that is intended to be arranged in the housing of a peristaltic pump for supporting and guiding the pump hose and at the same time providing lubricant primarily to the hose and the roller.
Embodiments of this aspect of the invention are evident from the accompanying dependent claims,
According to still another aspect of the invention is suggested a method to guarantee satisfactory lubrication of the hose and the roller in a peristaltic pump of mentioned type.
More specifically, it is suggested according to this aspect that an intermittent lubrication that is controlled by the engagement between the roller and the hose is accomplished by forming a lubricant reservoir in a yielding guide path for the hose.
Embodiments of this aspect of the invention are evident from the accompanying dependent claims.
These and other objects of the invention are achieved by the invention as defined in the appended claims.
Briefly, the present invention provides the following advantages:
The pump can be designed to be light and easily maneuverable, adapted to mobile equipment; while offering an
Improved possibility for interval lubrication of the hose and the roller;
Optimization of the suction capacity of the pump;
At least maintained discharge pressure capacity; and
Long useful life;
Allows comparatively simple mounting and dismounting of a very rigid hose in the pump.
Further objects, features and advantages of the present invention, as well as further embodiments thereof, are evident from the dependent claims and from the following description of exemplary embodiments.